This study was done to learn the following: Whether maintenance therapy can keep the viral load as low for as long protease inhibitor therapy does; Whether the drugs of the two maintenance therapies are safe and tolerable and whether there are fewer, different, or more toxicities when switching to maintenance therapy; and If the maintenance therapy stops working and viral load goes up, whether the protease inhibitor therapy taken before this study will work as well again. This study planned to use stavudine (d4T, Zerit), didanosine (ddI, Videx), efavirenz (EFV, DMP-266, SUSTIVA), and hydroxyurea (HUD, Droxia) in various combinations. The drugs d4T and ddI are nucleoside analogue reverse transcriptse inhibitors (NRTIs) and are approved by the FDA for treating HIV infection. The 200 mg tablets and the once-a-day dosing of ddI are investigational (not FDA-approved). HU is FDA-approved for treatment of some cancers and blood disorders. Its use in this study as an anti-HiV drug is investigational.